export let yzm = function () {
  let str = "";
  let str_list =
    "0123456789qwertyuioplkjhgfdsazxcvbnmQWEASDZXCRFVBGTYHNUJMKIOLP";
  let arr = str_list.split("");
  let i = 3;
  while (i >= 0) {
    let index = Math.round(Math.random() * arr.length);
    str = str + arr[index];
    i--;
  }
  return str;
};
